<template>
  <div class="pagination">
    <button
      :disabled="startEndPage.start === 1"
      @click="$emit('changePageNo', pageNo - 1)"
    >
      上一页
    </button>
    <button v-show="startEndPage.start > 1" @click="$emit('changePageNo', 1)">
      1
    </button>

    <button v-show="startEndPage.start > 2">···</button>

    <button
      v-for="page in StartEndArr"
      :key="page"
      @click="$emit('changePageNo', page)"
      :class="{ active: page === pageNo }"
    >
      {{ page }}
    </button>

    <button v-show="startEndPage.end < totalPages - 1">···</button>
    <button
      v-show="startEndPage.end < totalPages"
      @click="$emit('changePageNo', totalPages)"
    >
      {{ totalPages }}
    </button>
    <button
      :disabled="startEndPage.end === totalPages"
      @click="$emit('changePageNo', pageNo + 1)"
    >
      下一页
    </button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  mounted() {},
  props: ["pageNo", "totalPages", "continuePage", "total"],
  computed: {
    //当前展示的页码
    startEndPage() {
      const { totalPages, pageNo, continuePage } = this;
      let start = 0;
      let end = 0;
      //如果总条数小于展示页码的长度
      if (totalPages < continuePage) {
        start = 1;
        end = totalPages;
      } else {
        //如果总条数大于等于展示页码的长度
        start = pageNo - Math.floor(continuePage / 2);
        end = pageNo + Math.floor(continuePage / 2);
        if (start < 1) {
          start = 1;
          end = continuePage;
        }
        if (end > totalPages) {
          end = totalPages;
          start = totalPages - continuePage + 1;
        }
      }
      return { start, end };
    },
    //需要循环生成的button页码
    StartEndArr() {
      const arr = [];

      for (var i = this.startEndPage.start; i <= this.startEndPage.end; i++) {
        arr.push(i);
      }
      return arr;
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
